Add printf format checks to util's log functions

Add printf format checks to util's log functions

Add gcc printf format checks to all of the logging functions
defined in src/util/afsutil.h

Deal with the fallout, in particular create cast functions to go
from VolumeId and VnodeId to (unsigned int)

Change-Id: I28181b73cfeac22cf869d34e75a8335e65125e36
Reviewed-on: http://gerrit.openafs.org/793
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>